Many advanced aircraft configurations of current interest feature multiple control surfaces that need to be carefully scheduled for optimum performance. By way of example, for a candid controlled fighter configuration, the task may be to schedule canard and wing leading edge and trailing edge flaps for minimum trimmed drag at a cruise condition. When the surfaces to be scheduled are few, the determination of the optimum setting of the surface is simple. However, often there are many surfaces to be considered which compounds the problem. During aircraft configuration development decisions must be made as to the control surface deflections to be tested and built into the configurations. The task of determining the optimum setting is therefore complex and time consuming. There is also the need for some synthesis in terms of the control deflections of the performance effect of so many variables.
An optimization technique for assisting in the problems mentioned above encountered during aircraft design was published in a paper given at an AIAA Aircraft Systems and Technology Meeting, Aug. 20-22, 1979, and entitled "Application of Lagrange Optimization to the Drag Polar Utilizing Experimental Data" by J. S. Kohn, an employee of the present assignee. The paper is numbered 79-1833.
The Lagrange optimization used with linear aerodynamic theory to define optimum aircraft geometry is shown to have application to the determination of optimum control surface deflections as a function of angle of attack necessary to provide a maximum lift-drag deflection for a multiplane aircraft configuration. This optimization technique is suggested as a research tool in designing an aircraft configuration so that an optimized performance characteristic, such as minimum trimmed drag, may be accomplished at a particular condition, such as a cruise condition.